Notes on the Zoothera thrushes in the Tweed Range of north-eastern New South Wales

Abstract

The Zoothera thrush complex is represented on the Australian mainland by the Bassian Thrush Z. lunulata and the Russet-tailed Thrush Z. heinei. These species are sympatric at several locations on the eastern coast. Often, these populations occupy different elevations, with the Bassian Thrush preferring higher elevations, though reasons for this are poorly understood. I present data from automated acoustic recordings made of these species in the Border Ranges and Mebbin National Parks of north-eastern New South Wales between ~300 m and 1100 m above sea-level over a 1-year period from June 2015 to May 2016. Bassian Thrushes were recorded most frequently in October, typically at or above 900 m. Russet-tailed Thrushes were recorded most frequently in August, at or below 700 m. Differences in elevational preference between the species may be driven by several factors including adaptation to cold, avoidance of interspecific competition and avoidance of hybridisation.